Below Zero (2009)

A Joe Pickett novel from #1 New York Times-bestselling author C.J. Box.

Six years ago, Joe Pickett's foster daughter, April, was murdered. Now, someone is leaving phone messages claiming to be the dead girl. As his family struggles with the disturbing event, he discovers that the calls have been placed from locations where serious environmental crimes have occurred. And as the phone calls grow closer, so does the danger.